Decontamination Assessment of Nanofiber-based N95 Masks

Environmental Science and Pollution Research https://doi.org/10.1007/s11356-022-20903-w RESEARCH ARTICLE Decontamination Assessment of Nanofiber‑based N95 Masks Raheleh Faridi‑Majidi1 · Faezeh Norouz2 · Safieh Boroumand1 · Seyed Nasrollah Tabatabaei2 · Reza Faridi‑Majidi1,2 Received: 20 May 2021 / Accepted: 30 September 2021 © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2022 Abstract As the world battles with the outbreak of the novel coronavirus, it also prepares for future global pandemics that threaten our health, economy, and survivor. During the outbreak, it became evident that use of personal protective equipment (PPE), specially face masks, can significantly slow the otherwise uncontrolled spread of the virus. Nevertheless, the outbreak and its new variants have caused shortage of PPE in many regions of the world. In addition, waste management of the enormous economical and environmental footprint of single use PPE has proven to be a challenge. Therefore, this study advances the theme of decontaminating used masks. More specifically, the effect of various decontamination techniques on the integrity and functionality of nanofiber-based N95 masks (i.e. capable of at least filtering 95% of 0.3 μm aerosols) were examined. These techniques include 70% ethanol, bleaching, boiling, steaming, ironing as well as placement in autoclave, oven, and exposure to microwave (MW) and ultraviolet (UV) light. Herein, filtration efficiency (by Particle Filtration Efficiency equipment), general morphology, and microstructure of nanofibers (by Field Emission Scanning Electron microscopy) prior and after every decontamination technique were observed. The results suggest that decontamination of masks with 70% ethanol can lead to significant unfavorable changes in the microstructure and filtration efficiency (down to 57.33%) of the masks. In other techniques such as bleaching, boiling, steaming, ironing and placement in the oven, filtration efficiency dropped to only about 80% and in addition, some morphological changes in the nanofiber microstructure were seen. Expectedly, there was no significant reduction in filtration efficiency nor microstructural changes in the case of placement in autoclave and exposure to the UV light. It was concluded that, the latter methods are preferable to decontaminate nanofiber-based N95 masks. Keywords Face masks, nanofibers · Filtration efficiency · Pressure drop · Microstructure Introduction Face masks are among the most important personal protective equipment (PPE) that are proven to reduce transmission risks of infectious airborne particles (Paxton et al. 2020). Airborne particles containing hazardous pathogens such as harmful viruses can cause serious health concerns from mild symptoms to, in the case of SARS, MERS, or the recent SARS-Cov-2, acute illness and even death (Bałazy et al. 2006). In a recent study by Responsible editor: Lotfi Aleya * Reza Faridi‑Majidi 1 Fanavaran Nano-Meghyas (Fnm Co. Ltd.), Tehran, Iran 2 Department of Medical Nanotechnology, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences, Tehran, Iran Haung et al., ‘increased availability of PPE’ ranks among the top four effective government intervention tactics to combat COVID-19 (Haug et al. 2020). Masks are particularly important because they can both be used to protect the user from infectious airborne viruses as well as to prevent further spread of the virus from the infected user. However, in the midst of a pandemic, surging demand for masks has increased concerns about their adequate supply (Mackenzie 2020; Liao et al. 2020). To respond to the current global needs, various studies have examined a number of decontamination techniques for the purpose of reusing masks (Fischer et al. 2020; Grinshpun, Yermakov, and Khodoun 2020; O'Hearn et al. 2020; Probst et al. 2020; Rubio-Romero et al. 2020; Viscusi, King, and Shaffer 2007; Smith et al. 2020; Fischer et al. 2020; Lore et al. 2012; Viscusi et al. 2009; Bergman et al. 2010; Viscusi et al. 2011; Gertsman et al. 2020; Woo et al. 2012; Bopp et al. 2020; Lowe et al. 2020; Juang and Tsai 2020; Yang et al. 2020). While masks fabricated by the conventional 13 Vol.:(0123456789) Environmental Science and Pollution Research melt-blown technique (Sureka, Garg, and Misra 2020) are the subject of these studies, with the advent of nanofiber technology and their use in production of masks (Tebyetekerwa et al. 2020) and given the structural differences between the two, in this study changes in filtration efficiency, pressure drop, and microstructure of nanofiberbased masks post decontamination by chemical, irradiation, wet and dry heat are examined and discussed. Although many potentially hazardous airborne viruses are in the range of hundreds of nanometers (Leung and Sun 2020), for the most part they can only travel when they are suspended in relatively large liquid droplets (Fennelly 2020). That is why standard N95 masks are considered adequate to capture most airborne particles (Paxton et al. 2020; Leung and Sun 2020). According to the National Institute for Occupational Safety and Health (NIOSH) regulations, 42 CFR 84 (NIOSH 1997), N95 masks must be able to prevent travers of at least 95% of 0.3 μm sodium chloride (NaCl) aerosol Particulate Matters (PM) (Bałazy et al. 2006). In addition, the pressure drop across the filtration layer at 85 L.min-1 must be blow 350 Pa (Konda et al. 2020). While conventional N95 masks based on melt-blown fabrication technique are arguably ineffective for particle size range of 0.1-0.3μm (Bałazy et al. 2006), researchers have turned to nanofibers for their higher surface area and smaller pore dimensions which provide enhanced filtration efficiency (Bałazy et al. 2006; Zhang et al. 2016; Wang et al. 2017). As seen in figure 1, a nanofiber-based mask is consisted of up to five nonwoven layers of which the middle layer is coated with nanofibers. In this configuration, highly porous and uniform structure of nanofibers allow air molecules to easily pass through the layers and as the result, this type of filtration is associated with a considerable lower pressure drop and improved breathability (Zhu et al. 2017). Fig. 1  Structural layers of a nanofiber-based mask 13 Material and methods Treatment methods and related conditions employed in this study are tabulated below (see Table 1). This selection was inspired by several other studies that examined the integrity of melt-blown based N95 masks after decontamination. In this study, all disposable nanofiber-based N95 masks were provided by ®Rima (FNM, Iran). For every method, three masks were randomly selected and grouped. All masks in this investigation came from a same production batch. Treatment methods Chemical (n=6): The randomly selected masks were soaked in 70% ethanol (Pars, Iran) overnight to dry by air at room temperature (RT). In the case of bleaching, o (...truncated)